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VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 01:58pm 06 Nov 2011
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Hi Tinker
It is something I made years ago when I was fooling with steam, I have never seen anything on the net like it as it is a bit crude and simple with only two parts, I will do up a few sketches but cannot scan anything at the moment as this computer is a Win 7 and it wont work any of my scanners so will have to wait till I get a XP machine next week.
All the best
BobFoolin Around
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 09:01pm 06 Nov 2011
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Converting the 2-stroke petrol outboard engine over to a uniflow vapor engine. -
All your points are taken, but I don't think there will be nearly the problems you all assume. The concept here is to input the high pressure (250 to 400 psi) liquid PROPANE (not water steam) into the cylinder through the spark plug holes in the top of the cylinders and the entire engine and cylinder water jackets will be kept HOT by passing heated water through the entire engine via what is normally the cooling water circuit.
The exhaust ports that are high up in the cylinder will be blocked completely and the ports that were originally the inlet ports from the crank case are about 3/4 the way down the piston stroke near the bottom. If need be these ports can always be increased in flow by removing more material from them and possibly also shifting there top and bottom sections up/down in the cylinder (the ports are accessible from the outside of the engine by removing covers). reshaping and relocating the in/out ports of a 2-cycle petrol engine is a tried and true hop-up procedure for motorcycle and go-cart engines that I have done many times.
Any re compression of un-expelled exhaust vapor does cause a bit of a loss of efficiency but since this is a 2 cylinder engine with 180 deg offset crankshaft throws the opposite cylinders power stroke will still keep it turning.
The possible problem with liquid in the cylinder is also an easy one to compensate for, you simply add more thickness to the head gasket (or machine a bit off the top of the prominent intake fuel upwardly directing crown of each piston) to accommodate any excess fluid. This type engine is not relying on a high compression ratio to operate so the added space above the piston only effects efficiency a slight bit by requiring a tiny bit more vapor be introduced into the top of the cylinders.
I finally got the old engine apart without snapping off TOO many screws, the crank bearings are roller bearings so it may last a while being lubed only with oil flowing along with the exhausted vapor, have to run it to actually find out.
Don B - SUPER research, Nice to see that a system IS possible. That is the kind of info concerning solenoid operation that is really useful, thanks for the effort. Your voltage control is similar to something I did years ago but much more dynamic, my application only ran at relatively slow speed so worked fine using simple resisters and transistor switches. We were hitting 12 volt DC solenoids with short 100 volt opening pulses and using a resistor continuously connected to 24 volts DC as the pre-opening bias, to turn the solenoid off we shorted across it with another transistor. The high voltage pulses were HARD on the solenoids but they sure did open FAST but you could hear them all over the building when they did. Replacing solenoids was pretty much a weekly maintenance procedure but at the time it was the only way to boost the machine speed to increase the amount of movie film that could be duplicated through each machine (Bell & Howell model "C").
The following link goes to the top of page 7 of the ORC system discussion that I started on a biodiesel discussion forum, Stu A M has an ORC system running on butane using a rotary automotive SCROLL type refrigeration compressor in reverse. This looks far simpler than any approach using valving, you simply apply pressure to one port and the output pulley goes round-n-round and the lower pressure vapor comes out the other port. He is still in development but has it working for short periods at speed or longer periods at slower speed, he is still tweaking the size of his heat input and condensing output. He has several Youtube videos of the test system posted and there are links in the discussion posts.
Link to page 7 of discussion - http://biodiesel.infopop.cc/eve/forums/a/tpc/f/269605551/m/ 2551084412/p/7Edited by tim c cook 2011-11-08
Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190
Posted: 10:53pm 06 Nov 2011
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Hi Bob and Tim C
It is nice to see that there are at least two people who have not given up on this thread.
Thanks for the offer re information on your valve Bob. Like others, I would certainly be interested to know how it works. The only thing is that the valve that I need has to be able to have the advance and cut off angles independently adjustable.
I note that you describe it as a pressure balanced valve. This problem gave me some difficulty when I was developing my valve concept, as the angle changing spools that I wanted to use could have acted as pistons under pressure, and locked the valve up. My problem was solved by making the flow radial into and out of the rotating shaft, rather than axial. Each spool also has an external circumferential groove, which, apart from being needed for air flow, also has the secondary benefit that the pressure is the same on all sides of the spool, so that it is not significantly displaced from central by pressure forces.
The only problem that I see with my design is that the lip seals that I plan to use to seal the spools to the shaft may tend to be popped out by pressure leakage along the shaft. The design actually retains the seals, so I hope that this will not be a problem. The exterior circumference of the spools is sealed into the bearing chamber with O rings and, again, these are inherently pressure balanced.
All very hard to visualise without a diagram, and I apologise for this, and will post some diagrams when I have something better than crude mud maps.
Hi Tim C. Glad to hear that you are still persevering with your design. One of the problems that I have been grappling with is how to minimise the unswept volume in the inlet of my engine. This is, literally, the volume of the piping between the inlet valving and the spark plug hole. Too much volume will adversely affect engine operation. The thing is though that the unswept volume is also your safety margin in the event of any liquid in the cylinder at the end of the upstroke. This leaves it somewhere to go, and probably means that you won't need to increase the cylinder head gasket thickness. You could possibly also add a safety valve to your inlet piping. The spring loaded ones of the type mass produced for air compressors would probably be quite suitable once recalibrated to suit your inlet pressure.
Like you, I am looking to heat the cylinder and cylinder head to minimise condensation. For me, this involves wrapping copper tube around the cylinder fins and creating passages in the plate forming the cylinder head. The incoming steam will pass through the piping and passages before being admitted to the engine. I will probably also have to set up some warm through arrangement to achieve adequate cylinder temperatures before operating the engine on steam. Still thinking about this.
I will also have to insulate at least the cylinder and head, but possibly the crank case as well. I want to ensure that the steam loses as little temperature as possible through the engine, and that all of the condensation happens in the downstream heat exchanger and condensor.
One day maybe it will all come together.
Regards
Don B
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 05:24am 09 Nov 2011
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How about a steam turbine ?
Cheers, Tony.
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 09:11am 11 Nov 2011
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Warpspeed
Turbines use too much volume to be practical unless they are ginormous!
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:00pm 11 Nov 2011
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I am not so sure about that.
A few years ago I was involved with instrumenting a particular Solar project at RMIT in Melbourne.
Another different solar project they were doing there at the time, was a small turbine/generator powered by the temperature differential between the surface and bottom layers of a solar pond.
The reaction turbine design was particularly interesting, because it used rotating sonic nozzles in the style of a common lawn sprinkler.
The plan was that the whole thing was constructed into an evacuated, sealed, and submerged steel cylinder with an evaporator in the base, a turbine in the middle, and a condenser at the top.
It was designed to just sit there submerged in the pond generating power continuously from (relatively) low pressure low temperature steam day and night.
I have no idea how well it worked, or even if the project was ever completed and installed.
If it was, it may have been at one of the large experimental solar ponds at Alice Springs, but I really do not know.
But if you are really interested, try contacting Professor Akbar, dept of mechanical engineering, (building 7) RMIT for more details.
The simplicity of the whole scheme, plus the massive thermal storage of a solar pond should be ideal for generating constant fairly low level electrical power day and night throughout the entire year.
Not really sure of the power capability, but it may have been in the region of several tens of watts. All this must have been about twenty years ago, which is why I am a bit foggy on the details.
Edited by Warpspeed 2011-11-13Cheers, Tony.
Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190
Posted: 08:22pm 25 Jun 2012
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Rotary Inlet Valve Progress
After a nine month gap since my last post on this thread, I have finally got one rotary inlet valve completed and working on a single cylinder Briggs and Stratton test rig, plus further parts made ready to convert my three cylinder B&S engine from solenoid inlet valves to rotary ones.
The initial results from the single cylinder test rig are encouraging, although I am waiting on delivery of a contact tachometer to check the actual speed that it can achieve. It certainly appears that I can now at least get close to my target speed of 1,600 rpm.
If nothing else, I have demonstrated to my satisfaction that the valve permits me to independently adjust the lead angle (angle before top dead centre at which air or steam is admitted to the cylinder), and the cut off angle that determines how many degrees of rotation that air or steam is admitted to the cylinder. Both adjustments are essential for optimising the operation of a reciprocating air or steam engine.
In view of the considerable volume of posts already on this thread, I am thinking of posting details of this valve and the subsequent tests as a new topic (unless Glenn would prefer that this one continues).
Regards Don B
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:36pm 25 Jun 2012
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Great stuff Don.
Keep it coming !Cheers, Tony.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 09:19pm 25 Jun 2012
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Hi Don
Good to hear you are having success with the rotary valve, sometimes the old way is better than the new Hi tech.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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